Public interest in music apps continues to explode, with research firm Flurry Analytics recently reporting that sonically-inclined software programs are the second-fastest growing category of mobile applications in terms of overall time consumed by active users. Several eye-catching iPhone, iPod touch and iPad apps which expand mobile devices' functionality in new and novel ways may simply serve to underscore their rising popularity.

An extension of popular website WhoSampled.com, which lets listeners discern where song samples have been pilfered from, companion app WhoSampled scans your iPhone library to quickly reveal favorite tracks' family roots. Retailing for $2.99, it provides easily-digestible readouts of currently-playing or catalogued tunes' underlying or remixed samples, so you can discover new music, and the oft-overlooked historical origins of today's greatest hits. Original samples, which can be compared with their offspring, may also be enjoyed as YouTube snippets, and are accompanied by detailed notes outlining their presence, timing and relevance to borrowing tracks. Users may find it a convenient digital alternative to digging in the crates, with future ports to Android and other mobile platforms planned for release at a later date.

TastemakerX, billed as "the social game for music," goes a more interactive route, attempting to marry the recording business' ups and downs with the equally topsy-turvy vagaries of venture capital. Functioning like a virtual stock market, the free app (available on the iPhone and Web) effectively lets you buy and sell faux shares in top artists from Radiohead to Skrillex. Having planned a portfolio, players attempt to map picks with future market demand, with musicians' fortunes rising and falling based on in-app and real-world popularity. Successfully predict which acts that users will soon be clamoring for, and you can attract in-game followers, talk smack to friends or tout your hit-making abilities via images, geo-tags and snarky comments.

Developer Smule, known for its work on popular music apps I Am T-Pain and MadPad, has apparently also been bitten by the gaming bug, as evidenced by most recent release Beatstream for iPhone and iPad. Currently retailing for $0.99, the application is capable of turning music from your iTunes library into a playable rhythm game, with unique level layouts generated based on every track. Tapping in time with tunes, users essentially prod devices' touchscreens to swap the color of an arrow, which travels along a winding track, to match the hue of intervening barriers in time with tunes' beats. Albeit a simplistic alternative to set-top outings such as Rock Band and Guitar Hero, it compares favorably with mobile and handheld staples, e.g. the Tap Tap Revenge series.